Rainbow Electronics MAX1639 - Manual

________________General Description
The MAX1639 is an ultra-high-performance, step-down
DC-DC controller for CPU power in high-end computer
systems. Designed for demanding applications in which
output voltage precision and good transient response are
critical for proper operation, it delivers over 35A from 1.1V
to 4.5V with ±1% total accuracy from a +5V ±10% supply.
Excellent dynamic response corrects output transients
caused by the latest dynamically clocked CPUs. This
controller achieves over 90% efficiency by using synchro-
nous rectification. Flying-capacitor bootstrap circuitry
drives inexpensive, external N-channel MOSFETs.
The switching frequency is pin-selectable for 300kHz,
600kHz, or 1MHz. High switching frequencies allow the
use of a small surface-mount inductor and decrease out-
put filter capacitor requirements, reducing board area
and system cost.
Output overvoltage protection is enforced by a crowbar
circuit that turns on the low-side MOSFET with 100%
duty factor when the output is 200mV above the normal
regulation point. Other features include internal digital
soft-start, a power-good output, and a 3.5V ±1% refer-
ence output. The MAX1639 is available in a 16-pin
narrow SOIC package.
________________________Applications
Local DC-DC Converters for CPUs
Workstations
Desktop Computers
LAN Servers
GTL Bus Termination
____________________________Features
♦ Better than ±1% Output Accuracy Over
Line and Load
♦ Greater than 90% Efficiency Using N-Channel
MOSFETs
♦ Pin-Selected High Switching Frequency:
300kHz, 600kHz, or 1MHz
♦ Over 35A Output Current
♦ Resistor-Divider Adjustable Output from
1.1V to 4.5V
♦ Current-Mode Control for Fast Transient
Response and Cycle-by-Cycle Current-Limit
Protection
♦ Short-Circuit Protection with Foldback Current
Limiting
♦ Crowbar Overvoltage Protection
♦ Power-Good (PWROK) Output
♦ Digital Soft-Start
♦ High-Current (2A) Drive Outputs
MAX1639
High-Speed Step-Down Controller with
Synchronous Rectification for CPU Power
________________________________________________________________ Maxim Integrated Products 1
19-1337; Rev 0; 2/98
PART
MAX1639ESE -40°C to +85°C
TEMP. RANGE PIN-PACKAGE
16 Narrow SO
_______________Ordering Information
__________ Typical Operating Circuit
Pin Configuration appears at end of data sheet.
V CC
AGND
REF
FREQ
CC1
CC2
DL
PWROK
LX
BST
DH
PGND
TO V DD
CSH
OUTPUT
1.1V TO 4.5V
INPUT
+5V
V DD
CSL
FB
MAX1639
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
EVALUATION KIT
AVAILABLE